Power management is utilized in a mobile device to minimize the power consumption of the overall system, which can extend battery life and prevent overheating the device. For example, power management has been introduced for single burst transmissions in digital video broadcasting-handheld (DVB-H) handsets.
The DVB-H codec implements multiprotocol encapsulation (MPE), MPE forward error correction (MPE-FEC), and time slicing as a part of its power management scheme.
Time slicing comprises the transmission of data traffic in bursts followed by periods of no transmissions. The burst transmissions are referred to as time slices. In order to reduce the power consumption of the DVB-H handset, the DVB-H handset can shut down the receiver in between the time slices.
In a typical DVB-H communication, multiple input streams are received by different sources as individual elementary streams. The input streams are multiplexed according to a selected time slicing method. MPE-FEC coding, which provides an additional layer of error correction, is performed separately for each individual elementary stream. The system then performs MPE encapsulation of the data packets and embeds them into a transport stream.
FIG. 1 shows the power consumption stages during the reception of a single burst by a DVB-H handset. The power management is divided into the four power stages RF_ON, RF_OFF1, RF_OFF2, RF_OFF3. A fifth stage, the STANDBY stage is not shown. Table 1 is a description of the five power stages.
TABLE 1Power StageDescriptionRF_ONThe RF part is active and DVB-H demodulation is active.The wanted time-sliced burst transmission is received.RF_OFF1The RF part is shut down. MPE-FEC calculation isongoing. IP packets with no errors can be forwarded beforeMPE-FEC calculation is finalized.RF_OFF2The MPE-FEC calculation is finished. DVB-H handset isfeeding data for application engine.RF_OFF3The data transfer to application engine is finished and theDVB-H handset is waiting for the next burst transmission.STANDBYThe DVB-H application is not used. The DVB-H handset isin the standby stage waiting for a wake command.
FIG. 2 shows the power stages during reception of a single burst transmission with detected MPE-FEC errors. The RF_ON mode is further divided into two stages, the demodulator re-synchronization (re-sync) stage and the demodulation (demod) stage. During the re-sync stage, an analog-to-digital converter, automatic gain control, tuner, and core processor are all operating. During the demod stage, the analog-to-digital converter, automatic gain control, tuner, core processor, multistream transport processor (MTSP, the MFEC decoder and CRC modules are all operating. When there are detectable errors in the MPE-FEC table, the RF_OFF1 stage is further divided into a transport stream filtering (TS-filter) stage, an MPE-FEC decoding (mdecod) stage, and an MDATATRANS stage. During the TS-Filter stage, the MTSP, MFEC, and CRC blocks are all operating. During the mdecod stage, an RE decoding module is operating. Finally during the MDATATRANS stage, the IP datagram is operating.
FIG. 3 shows the power stages during reception of a single stream transmission where no MPE-FEC errors have been detected. An analog-to-digital converter, automatic gain control, and tuner/PHY core consume power during re_sync stage and demod stage. The processor, the MFEC decoder and other devices consume power during the demod stage and the TS-filter stage.
FIG. 4A and FIG. 4B together comprise a flow diagram of a top level power management method for a DVB-H handset receiving a single burst transmission. The handset power is activated (401). The program specific information/service information (PSI/SI) is collected (403). The handset then searches for a network (405). If no network is located, a “No Network” message is transmitted to the host (407). Otherwise, if a network is located, the handset determines whether the first time slice is received successfully (409).
If the first time slice is not received, the handset transmits an error message to the host (411). If the first time slice is received successfully, then the handset extracts the arriving time of the next time slice (413). The handset then estimates the resynchronization time and sets the power management timer (415). Next, the handset enters standby stage (417). The handset waits in standby stage, until the power management timer expires, a message is received from the host, or an interrupt is received (419). If the power timer expires, the handset enters re_sync stage (421), then demod stage (423), then TS-filter stage (425), then mdecod stage (427) and then MDATA Trans stage (429). However, if the handset receives a message from the host or an interrupt, the handset activates the message/interrupt handler (431). The handset then determines whether the message or interrupt handling can be performed within a meaningful power off period (433), and if so, then the handset returns to standby stage (417). If interrupt handling cannot be performed within a meaningful power off period, then the handset operates on full-power-stage until it receives the next burst successfully (435). During the full-power stage both the tuner and demodulator remain on.
In addition to receiving single stream transmissions, the DVB-H Guidelines also support the reception of multiple elementary streams embedded in the same burst as well as multiple services embedded in the single elementary stream. Accordingly, the power management scheme presented in the DVB-H Implementation Guidelines supports the reception of multiple channels on the same device, provided that all required services are on located in concurrent streams or adjacent (i.e. contiguous) burst transmissions, as shown in FIG. 5 and FIG. 6 respectively.